Number Blocker by HQTelecom.com - Version 6 High Volume Blocking Capacity: Block up to 1,000 unwanted phone numbers Block calls showing as OUT OF AREA (--- O ---), PRIVATE (--- P ---) or with no phone number displayed Block up to 5 area codes or prefixes (1-5 digits) - No initial setup required (just plug and start blocking) One-Button Operation - Simply press BLOCK button to block unwanted numbers Compatible with standard (PSTN) single lines & VoIP services